What are run-flat tires?

We’ve gotten a few questions recently from readers who are curious about run-flat tires and exactly how they work. So we’ll dedicate today’s post to explaining the concept behind run-flat technology.

First off, the point of a run-flat tire is to – you guessed it – allow the car to keep driving (albeit at reduced speeds and for shorter distances) after it has begun to lose pressure from a puncture. Most run-flat tires allow vehicles to maintain approximately 55 mph even while losing air, for distances of up to 100 miles. Run-flat tires are popular in smaller sports cars that don’t have room for spares, as well as in high-end and luxury cars for added convenience and safety.

There are three types of run-flat tires. Self-supporting run-flats employ a thicker sidewall that can carry the weight of the car even if the air pressure inside the tire drops dramatically. These types of run-flat tires are common on light trucks and passenger cars. They can support a vehicle at 50mph for up to 50 miles, though anything more than this usually results in irreparable damage.

The second type of run-flat is the self-sealing configuration. These tires contain an extra lining that self-seals after a puncture from a nail or other sharp debris. This prevents air from escaping the tire at all, or at the very least, much slower than it normally would after being punctured.

The final and least popular method is the auxillary supported run-flat. These make use of an extra support ring attached to the wheel which can support the weight of the car in the event of a flat tire. Because these systems require custom tires AND wheels, they are often deemed too expensive for widespread usage.

Because run-flat tires usually cost more than regular replacement tires, they represent less than 1% of the aftermarket tires sold today. In the same vein, they are almost never used as original equipment tires. Many people also steer clear of run flats because they are heavier and may provide more rolling resistance, thus decreasing gas mileage. But for those who want additional safety and convenience and don’t mind paying for it, run-flat tires are a great investment.